Loose seat post - will I damage my frame?

My old Kona Coiler frame takes a 30mm seatpost. A 30mm post fits perfectly. You have to wiggle it around a little to move it up and down, but no force is required.

I got a 27.2mm gravity dropper and a 27.2mm - 30mm shim. I thought that combination would be right, but it's loose. If I release the clamp it instantly falls straight down. When tight, the seat post doesn't make contact with the entire circumfernce of the shim.

Have I got a dodgy shim, or is that normal when using a shim? The shim is not a gravity dropper branded shim. Is there something different about the gravity dropper ones? They didn't have any in stock when I placed the order.